1. Field of the Invention
The present invention pertains to a method and apparatus for continuous downhole release of fluid(s) in oil or gas wells. More particularly, the present invention pertains to a method and apparatus for continuous downhole release of fluid in oil or gas wells using wireline, including slickline, electric line and/or braided line.
2. Description of the Prior Art
In the oil and gas industry, it is common to introduce fluids into oil or gas wells. Such fluids, which are frequently used during both drilling and production phases, include, but are not limited to, acids, surfactants, corrosion inhibitors and/or other additives or chemicals aimed at improving the drilling process and/or the producing characteristics of a well. Frequently, such fluids can be pumped down a well from the earth's surface and commingled with other fluids in such well. However, in other situations, it is advantageous to introduce such fluids at or near the bottom of a well; that is, the subject fluids are kept isolated from other fluids until they are released into the wellbore environment at a desired downhole location.
As existing oil fields mature, it is becoming increasingly common to inject beneficial chemicals and/or other additives into older oil and gas wells. Hydrocarbon production often decreases in such mature wells while associated salt water production increases. In many cases, this phenomenon is coupled with a decline in reservoir pressure required to lift produced fluids (including the heavier saltwater) from the bottom of a well to the surface. As water production increases, and reservoir pressure decreases, hydrocarbon production is frequently “choked off” and greatly diminished. As a result, it is often desirable to increase the overall production rate from such wells in order to improve recovery of hydrocarbons from the well stream.
One method commonly used to maximize production involves introduction of soap, foaming agent(s) or other similar additive(s) into producing wells in order to create foam. Such foam has the effect of reducing the hydrostatic head created by relatively heavy wellbore fluids such as saltwater. As foam is created and hydrostatic head is reduced, the existing formation pressure has significantly less resistance to overcome, thereby resulting in higher overall producing rates. As such, more overall fluid (and, thus, greater volumes of hydrocarbons) can be produced from such wells, and the wells can produce longer prior to depletion.
In order to generate the greatest reduction in hydrostatic head, it is generally beneficial to introduce such foaming agent at a downhole location near the point that formation fluids enter a wellbore. In most cases, this point is adjacent to, or in general proximity to, the production perforations in a well. Frequently, such production perforations are located at or near the bottom of a wellbore.
Capillary strings are often utilized to carry such foaming agent(s) into a wellbore and release same in the wellbore environment at an optimum down hole location. Such capillary strings prevent undesired commingling of fluids and/or premature foaming action. Such capillary strings, which typically consist of relatively small diameter pipe, can be concentrically disposed within the production tubing of a well. Such capillary strings often extend from the surface of a well to a point at or near the perforations of such well. Although such capillary strings can be made from jointed pipe, in most cases such capillary strings consist of continuous lengths of pipe. Such continuous pipe typically arrives at well sites on spools or coils and it thereafter straightened during the installation process.
Generally, foaming agent(s) and/or other chemicals are pumped down the internal diameter of a capillary string. While inside the capillary string, such foaming agent(s) and/or chemicals remain isolated from other fluids in the wellbore environment. However, when said foaming agent(s) and/or other chemicals reach the lower terminus of the capillary string, the foaming agent(s) and/or other chemicals flow out of said capillary string and come in contact with wellbore fluids, including saltwater. Ideally, such foaming agent(s) and/or other chemicals will mix with such wellbore fluids and generate foam, thereby reducing the hydrostatic head exerted by such wellbore fluids. Because the hydrostatic head of the saltwater is reduced, greater volumes of wellbore fluids (including hydrocarbons) can be produced up the annular space existing between the outer surface of the capillary string and the inner surface of the surrounding production tubing.
Although use of capillary strings in this manner can frequently increase hydrocarbon production, in most cases such capillary strings can be expensive to purchase and install. Moreover, in certain circumstances, wells which initially appear to be ideal candidates for installation of capillary strings do not realize the anticipated results following actual installation of such capillary strings. As such, it is advantageous to have an efficient and inexpensive means of evaluating whether installation of such capillary strings will yield positive results before incurring the expense associated with such actual purchase and installation of such capillary strings.